Statistical techniques such as Gaussian process (GP) regression have been used by treating stellar activity behavior as a quasi-periodic signal [1]}, [2]}, [3]}. This approach may sometimes lead to better precision and accuracy of planetary parameters, especially those in the lower-mass regime [4]}, [5]}.
Likewise, these signals can be wavelength-dependent, usually with the amplitude decreasing in the redder regime of the spectrum, but still containing some residual effect depending on the star-spot configuration and temperature difference [6]}.
For this reason, there is a push for higher-precision instruments covering the red and near-IR wavelength range such as CARMENESCalar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Échelle Spectrographs, http://carmenes.caha.es [7]}, [8]}, GIARPSGIAno & haRPS-n, https://www.tng.inaf.it/news/2017/04/04/giarps/ [9]}, HPFThe Habitable Zone Planet Finder, https://hpf.psu.edu/ [10]}, [11]}, IRDInfraRed Doppler instrument [12]}, [13]}, [14]}, MAROON-XRed-optical, high-resolution spectrograph with focus on mid- to late-type M dwarfs, https://www.gemini.edu/instrumentation/maroon-x/ [15]}, [16]}, and SPIRouA near-infrared spectropolarimeter/velocimeter, https://spirou.omp.eu/ [17]}.
